i don't think you should sell it.
i'm not a fan of graffiti or custom paint on a boombox. but, what you bought, isn't a boombox. it's movie memorabilia. a display piece. like art. that's why it came with a certificate of authenticity. it'll be tough (and pointless) to expect to flip it quick and make money on it. memorabilia is more like investing; whether it's elvis's pink cadillac, or a baseball signed by babe ruth.
and i'm sorry, but, if you don't know what harold & kumar is, you're just not with the times. old movies like "breakin" are just as gay as their modern day counterparts like "you got served".
quit worrying about what people think, chris. and start printing out flyers for your own bottomless party!